This invention relates to rechargeable nickel ion batteries with high capacity.
There exist six types of small and portable batteries, including Zn—Mn batteries, NiMH batteries, NiCa batteries, lithium-ion batteries, lead-acid batteries and zinc-ion batteries. Among them, Zn—Mn batteries are primary batteries and cannot charge/discharge repeatedly; the other batteries, as secondary batteries, are rechargeable. Secondary batteries make the most of raw materials, thus are more economical and functional; however, their service life is generally several hundred cycles, which means that the batteries need to be replaced after using period of time.
Previous patent application (CN 201010297235.3) invented a rechargeable nickel ion battery, which uses α-MnO2 as cathode, nickel as anode and nickel ion aqueous solution as the electrolyte. The battery chemistry of nickel ion battery is written as:cathodic reaction: xNi2++2xe−+MnO2↔NixMnO2  (1); andanodic reaction: Ni↔Ni2++2e−  (2).
The nickel ion battery is low-cost, safe and environment-friendly, but its MnO2 cathode has a low capacity of 80 mAh g−1. As is known to all, high capacity is the necessary prerequisite to the practical application of batteries. Therefore, the enhancement of battery capacity should be achieved by searching for new electrode materials with higher capacity.
Graphene and carbon nanotubes (CNTs) are nano-carbon materials with unique structures. Graphene is constructed by single or multi layers (usually less than 10 layers) of carbon atoms, while CNTs are formed by curled graphite sheets. Unique structures result in special properties of the above materials. Graphene and CNTs, as energy storage materials, have been widely utilized in Li-ion batteries and supercapacitors, showing a very high capacity of 300-1000 mAh g−1. This patent reveals a rechargeable nickel ion battery with graphene cathode or CNT cathode. By storing nickel ion, graphene and CNTs can deliver a capacity of 500 mAh g−1, which is six times larger than MnO2 cathode capacity, therefore, capacity of nickel ion battery is enhanced.